Mobile communications systems provide mobile users with means to communicate from an arbitrary location within a Public Land based Mobile Network PLMN. Initially, mobile communications systems offered more or less the same services as do wired communications systems, i.e. voice calls, data calls and fax calls. The ever-changing location of the mobile user was not seen as a useful piece of information, which the wired communications systems cannot deliver. A more valid vision is that by making full use of the user's location information, mobile communications systems can achieve competitive advantages over wired communications systems. This information can be used for customizing certain value-added services according to the user's location. Such location-specific value-added services include localised weather forecasts, entertainment programs, timetables, navigation and locating a mobile user in an emergency. Additionally, the users location can also be used for law-enforcement purposes.
Within the context of this application, the following conventions will be used. Location management refers to the task of tracking a user equipment's location in terms of location/routing areas and cell/network element identifiers. Thus, location management is performed in any mobile communications system, and it is a necessary task for routing calls to a mobile subscriber. In contrast, location services, LCS, refer to the task of tracking a user equipment's location in terms of geographical coordinates. This task is not necessary for routing calls. Rather, it is a value-added information service, or it can be used for producing value-added services.
According to the state of the art of location services in the CS (Circuit-Switched) domain, it is possible for the network (MSC, Mobile Services Switching Centre) to request a subscriber to accept or reject that the location of the mobile telephone is revealed to an LCS Client. However, a corresponding mechanism does not yet exist in the UMTS (Universal Mobile Telecommunications System) packet-switched domain or in the GPRS (General Packet Radio Service) system.
In the circuit-switched domain MSC uses supplementary services signalling for invoking the privacy request. This is not a possible solution in the packet-switched domain, since supplementary services and corresponding signalling are not seen very useful in the packet-switched domain.